Bird Networks in the Amazon (complexity)
Relationships between organisms are broad
- Competition
- today
- Mutualisms
- jigsaw
- Predation and Consumption
- next week
- Parasites and hosts
- Humans vs other species
- friday data exercise
What is competition?
Species relationships may have benefits/costs to fitness
WHO: Intra vs Inter-specific competition
Intraspecific competition limits population growth
Competition is a powerful driver of evolution
- Natural selection favors individuals that do not compete
- Drives niche separation, specialization and species diversification
- Directional selection can occur causing character displacement
Gause’s Law: Theory of Competitive Exclusion
- Two species cannot occupy the same niche if they need the same resource
- Species cannot coexist at constant populations
- winner and loser
- Leads to local extinction of weaker competitor or shift to a different ecological niche
Gause’s test tube Paramecium study
Red vs Grey Squirrel in Britain (Murphy 2015)
Competitive exclusion, however, is rare in nature
- Resources are variable/limiting in an environment
- leads to symmetric competition
- Species compete for multiple resources
- exclusion based on a single resource is too simple
- Complete niche overlap (test tube) is rare
- TAKE HOME: Greater overlap = greater competition
Competition does result in the ‘Realized Niche’
Joseph Connel: Competition among barnacles
Can’t we all just get along?
Co-existence and natural selection
- Overlapping species evolve to use a niche differently
- resource partitioning = division of resources
- Species whose niches only partly overlap coexist easier
- use the environment differently (niche differentiation)
- evolve traits to use different/less overlapping resources (character displacement)
- Co-existing species can overlap by using different forms of resources (niche complementarity)
Co-existence through resource partitioning in birds
Co-existence through resource partitioning in lizards
Niche complementarity: different use of microhabitats
Coexistence and character displacement:
